Diseases relating to brain function, such as Alzheimer's disease, are becoming a worldwide problem, and Japan, which is fast becoming an aging society, must urgently solve the issue of overcoming those diseases. There are said to be about 20,000,000 patients of Alzheimer type cognitive disorder in the world, and in Japan, 40% or more of the about 1,500,000 cognitive disorder patients are presumed to have Alzheimer type cognitive disorder.
Donepezil hydrochloride (Aricept (Registered Trademark)), which is an cholinesterase inhibitor, is used widely as a powerful means of treating Alzheimer's disease, and a new acetyl cholinesterase inhibitor is approved for production. However, the efficacy ratio of the clinical result of donepezil hydrochloride is about 50%, and a stronger and safer agent is awaited.
Exploration and research for a new pharmaceutical agent aimed at improving brain function by a new action mechanism is also under way. For example, ZSET1446 having an acetylcholine liberator effect and nefiracetam having a N-methyl-D-aspartate (NMDA) receptor activating effect have been reported, and clinical tests have been performed (Patent Documents 1 and 2, Non-Patent Documents 1 to 4). However, there is currently no new pharmaceutical agent approved for production other than acetyl cholinesterase inhibitor, and a strong desire exists for development of a new pharmaceutical agent having an action mechanism differing from existing pharmaceutical agents.
Further, the main accessory symptom for high-level brain dysfunctions including mental disease (schizophrenia, bipolar disorder, depression, phobia, sleep disorder, drug dependence, etc.), pervasive developmental disorder (autism, Asperger's syndrome, mental deficiency, polyergic disorder, tic disorder, etc.) is cognitive dysfunction. The prognosis of the disease is known to improve by a remedial teaching-based cognitive function improvement method, but development of an effective cognitive function improving agent is strongly awaited.